Objective: Depressive symptoms are common following acute coronary syndrome (ACS) and predict subsequent cardiovascular morbidity. Depression in acute cardiac patients appears to be independent of clinical disease severity and other cardiovascular measures. One factor that has not been considered previously is anaemia, which is associated with fatigue and adverse cardiac outcomes. This study assessed the relationship between anaemia on admission and depressive symptoms following ACS. Design: Longitudinal clinical observational study. Setting: Coronary care unit. Patients: 223 patients with documented ACS. Main outcome measures: Depressive symptoms measured with the Beck Depression Inventory 3 weeks after admission. Results: Anaemia was defined with WHO criteria and was present in 30 (13.5%) patients. Anaemia predicted raised depression scores 3 weeks later independently of age, gender, marital status, educational attainment, smoking, Global Registry of Acute Cardiac Events (GRACE) risk scores, negative mood in hospital and history of depression (p=0.003). The odds of a Beck Depression Inventory score ≥10 among anaemic patients were 4.03 (95% CIs 1.48 to 11.00), adjusted for covariates. Sensitivity analyses indicated that effects were also present when haemoglobin was analysed as a continuous measure. Anaemia also predicted major adverse cardiac events over the subsequent 12 months. Conclusions: Anaemia appears to contribute to depression following ACS and is associated with future cardiac morbidity. Studies evaluating the effects of anaemia management will help delineate the role of this pathway more precisely.